Minister Oliart's report gave gruesome details of a colonels' coup that had been planned for the day before national voting. The coup would have followed classical third-world strategy: More than 500 pages of detailed plans plotted out the meticulous takeover of all military headquarters, both in Madrid and the different regions. In addition, the palace of King Juan Carlos would have been forcefully ''neutralized'' along with the premier's palace, government ministries, and all centers of military and civilian power by approximately 70 small commando units working in coordination.

There were even long lists of civilians and high military officers to be ''neutralized,'' which in euphemistic military jargon is taken to mean on-the-spot execution if resistance to arrest is offered.

When the plot was uncovered Oct. 2, only three colonels were arrested and the ringleaders of last year's coup were shipped off to different provinces incommunicado. In spite of earlier promises, no further arrests have been announced, although numerous military and civilian suspected plotters are ''being investigated,'' the defense minister affirmed.

Unlike last year's coup attempt, in which only parliament was occupied, this coup plot was ''far more advanced and worked out,'' according to Oliart. ''There is no doubt that the plot had a sufficient degree of development to be carried through,'' he added gravely.

The uncomfortable feeling that there may be more coups to come has dominated the political campaigns.

''Unless all those implicated in the plot are themselves 'passively neutralized' by the government,'' affirmed a worried Felipe Gonzalez, leader of the opposition Socialist Party, which is expected to win the coming elections, ''democracy is in serious danger.''

''If they can't yet be arrested for lack of evidence or continuing investigations,'' continued Gonzalez, ''then at least they should be separated from responsible positions within the military.''

Right-wing leader Manuel Fraga of Popular Alliance caused outrage when he affirmed that, given the present situation in Spain, he could understand the plotters, although he does not justify their actions. He dismissed fear of another coup attempt as ''a mere fairy tale.''

In private dealings, Spanairds are worried. Conversations of ''where were you in the February coup'' gradually turn into serious discussions of what to do in the next coup, where to send the children, what embassy or what flight out of the country would be the best, and so on.

Although most prominent leaders insisted they would not leave the country, many families did consider seriously future exile. ''The best time to leave is in the first hours,'' this reporter was told by a neighbor.

It is still early to guess the electoral effect of the last coup trauma. Initially, it was thought to subtract votes from an assumed Socialist victory.

But Luis Solana, a Socialist member of parliament and spokesman on military affairs, commented that the effect may be the opposite.

''People realize that a strong government can best handle the military, and right now the Socialists offer just that: stability and a strong majority party. . . . A government that can't govern would be an example of the failure of democracy for the ultra-right-wing minority of the armed forces.''

Solana estimated that approximately 5 percent of the armed forces would be in favor of a coup. ''But that 5 percent means about 2,000 officers who can do a lot of damage unless they are removed from responsible positions.''